Illuminated multilayer structure with embedded light sources

ABSTRACT

A multilayer assembly for an electronic device includes a substrate film configured to accommodate electronics on at least first side thereof, a number of light sources on the first side of the substrate film and configured to emit light of predetermined frequency or frequency band, a plastic lightguide layer molded onto the first side of the substrate film and at least partially embedding the light sources, the plastic lightguide layer being of optically at least translucent material, and a masking layer provided on the outer surface of the plastic lightguide layer, wherein the masking layer defines a window for letting light emitted by the embedded light sources and propagated within the plastic lightguide layer to pass through the masking layer towards the environment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/155,956 filed Oct. 10, 2018, which is a continuation of PCTApplication No. PCT/FI2017/050259 filed. Apr. 11, 2017, which claims thebenefit of U.S. Provisional Application No. 62/321,769 filed Apr. 13,2016. The entire disclosure of each of the above-identified applicationsare incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

Generally the present invention relates to multilayer structures inconnection with electronics, associated devices, and methods ofmanufacture. In particular, however not exclusively, the presentinvention concerns provision of integral illumination solution within amultilayer structure.

BACKGROUND

Generally there exists a variety of different stacked assemblies andstructures in the context of e.g. electronics and electronic productssuch as various electronic devices.

The motivation behind stacking electronics and other elements in acommon structure may be as diverse as the related use contexts.Relatively often size savings, weight savings, cost savings, usabilitybenefits, or just efficient integration of components in terms of e.g.the manufacturing process or logistics is sought for when the resultingoptimized solution ultimately exhibits a multilayer nature. In turn, theassociated use scenarios may relate to product packages or food casings,visual design of device housings, wearable electronics, personalelectronic devices, displays, detectors or sensors, vehicle interiors,antennae, labels, vehicle and particularly automotive electronics, etc.

Electronics such as electronic components, ICs (integrated circuit) andconductors may be generally provided onto a substrate element by aplurality of different techniques. For example, ready-made electronicssuch as various surface mount devices (SMD) may be mounted on asubstrate surface that ultimately forms an inner or outer interfacelayer of a multilayer structure. Additionally, technologies fallingunder the term “printed electronics” may be applied to actually produceelectronics directly and additively to the associated substrate. Theterm “printed” refers in this context to various printing techniquescapable of producing electronics/electrical elements from the printedmatter, including but not limited to screen printing, flexography, andinkjet printing, through a substantially additive printing process. Theused substrates may be flexible and printed materials organic, which ishowever, not necessarily always the case.

A substrate such as a plastic substrate film, may be subjected toprocessing, e.g. (thermo)forming or molding. Indeed, using e.g.injection molding a plastic layer may be provided on the film,potentially then embedding a number of elements such as electroniccomponents present on the film. The plastic layer may have differentmechanical, optical, electrical, etc. properties. The obtainedmultilayer, or stacked, structure may be configured for a variety ofpurposes depending on the included features, such as electronics, andthe intended use scenario and related use environment. It may, forinstance, comprise connecting features such as fluke type protrusionsfor coupling with compatible recesses of a host element or vice versa.

Occasionally different elements, surfaces or devices should be providedwith illumination capability that may bear e.g. decorative/aesthetic orfunctional, such as guiding or indicative, motive. For example, theenvironment of the element or device should be floodlit for increasingvisibility in the gloom or dark during night-time, which may, in turn,enable trouble-free performing of various human activities typicallyrequiring relatively high lighting comfort, such as walking or reading,to take place. Alternatively, the illumination could be applied to warnor inform different parties regarding e.g. the status of the hostelement or connected remote device via different warning or indicatorlights. Yet, the illumination might yield the host element a desiredappearance and visually emphasize its certain features by providing e.g.brighter areas thereon with desired color. Accordingly, the illuminationcould also be applied to instruct a user of the device about e.g. thelocation of different functional features such as keys, switches,touch-sensitive areas, etc, on the device surface, or about the actualfunction underlying the illuminated feature.

Thus, there are a great number of use cases for illumination inconjunction with different structures and devices. As the illuminationmay not, however, always be a critical or sole feature of highestpriority or of most importance in the associated product, and it mayactually be considered a supplementary, optional feature only, thedesign and implementation of lighting features providing the desiredillumination effect shall be duly executed. Weight and sizerequirements, elevated power consumption, additional designconsiderations, new process steps, and generally increased overallcomplexity of the manufacturing phase and the resulting product are allexamples of numerous drawbacks easily becoming materialized as a sideeffect of adopting lighting features in the target solution. Yet, theappearance of the lighting effect and e.g. perceivability of lightingelements is one other issue. In some applications, the light sourcesshould remain hidden or weakly exposed, or the lighting effect should berather delicate without hotspots.

SUMMARY

An objective of the present invention is to at least alleviate one ormore of the above drawbacks associated with the existing solutions inthe context of various electronic devices or other host elements thatare to be provided with lighting features.

An objective is achieved with the embodiments of a multilayer assemblyand a related method of manufacture in accordance with the presentinvention.

According to one embodiment of the present invention, a multilayerassembly for an electronic device comprises

a preferably flexible substrate film configured to accommodateelectronics, such as conductive traces and electronic components, e.g.SMDs (surface-mount device), on at least first side thereof, said filmhaving the first side and a second side,

a number of light sources, preferably LEDs, provided on the first sideof the substrate film and configured to emit light of predeterminedfrequency or frequency band, preferably including or substantiallylimiting to visible light,

a molded plastic lightguide layer provided onto the first side of thesubstrate film and at least partially embedding the light sources, theplastic lightguide layer being of optically at least translucent,optionally transparent, material having regard to the predeterminedfrequency or band, wherein the plastic lightguide layer is configured totransmit light emitted by the embedded light sources so that thetransmitted light propagates within the lightguide layer and isoutcoupled from the plastic lightguide layer via an outer surfacethereof substantially opposite to the embedded light sources,

a masking layer provided on the outer surface of the plastic lightguidelayer, containing substantially opaque material to block external viewof at least some internals of the multilayer structure including thelight sources, wherein the masking layer defines a window for lettingthe light emitted by the embedded light sources and propagated withinplastic lightguide layer to pass through asking layer towards theenvironment, and

at least one diffusor located between the light sources and theenvironment,

the light sources, masking layer and related window being mutuallyconfigured such that there is no direct line-of-sight (LOS) path atleast within a selected viewing angle from outside the assembly,preferably including zero angle from the surface normal of the maskinglayer, to the light sources and optionally further electronics throughthe window.

According to one other embodiment, a method of establishing a multilayerassembly for an electronic device comprises

obtaining a preferably flexible substrate film configured to accommodateelectronics on at least first side thereof, said film having the firstside and a second side,

providing a number of light sources on the first side of the substratefilm, said light sources being configured to emit light of predeterminedfrequency or frequency band,

molding a plastic lightguide layer onto the first side of the substrateand thereby at least partially embedding the light sources, the plasticlightguide layer being of optically at least translucent, optionallytransparent, material having regard to the predetermined frequency orband of light, wherein the plastic lightguide layer is configured totransmit light emitted by the embedded light sources so that thetransmitted light propagates within the lightguide layer and isoutcoupled from the lightguide layer via an outer surface thereofsubstantially opposite to the embedded light sources, and

providing a masking layer on the outer surface of the lightguide layercontaining substantially opaque material to block external view of atleast some internals of the multilayer structure including the lightsources, wherein the masking layer defines a window for letting thelight emitted by the embedded light sources and propagated within thelightguide layer to pass through the masking layer towards theenvironment,

wherein at least one diffusor is provided between the light sources andthe environment, the light sources, masking layer and related windowbeing mutually configured such that there is no direct line-of-sightpath at least within a selected viewing angle from outside the assemblyto the light sources and optionally further electronics through thewindow.

A device such as an electronic device comprising an embodiment of theassembly may be provided. The device may be a portable, hand-held,wearable, desktop or other type of a device.

It may be of stand-alone type or the device may constitute a part of alarger ensemble with reference to a dashboard of a vehicle, for example.

Different considerations presented herein concerning the embodiments ofthe assembly may be flexibly applied to the embodiments of the methodmutatis mutandis, and vice versa, as being appreciated by a skilledperson.

The utility of the present invention arises from a plurality of issuesdepending on the embodiment.

Lighting features such as light sources and associated optics, guidinglayers, lenses, diffusers, collimators, prisms, diffracting elements,reflectors, opaque/masking elements, etc. may be cleverly integratedinto a common assembly, which may in turn establish at least part of ahost device or host element. The applicable light sources includedifferent printed light sources such as OLEDs and more traditionalmountable components such as LEDs, both alike. The illumination effectthus created may bear aesthetic/decorative, indicative, instructiveand/or warning functions, for example. By the proper configuration ofthe light sources, intermediate elements and the window, including e.g.the positioning of the masking layer in relation to the embedded lightsources and lightguide layer, the outcoupled light may appear veryuniform while the masking layer conceals the hideous electronics such asthe light sources from the external viewer.

Yet, the assembly may exhibit a selected appearance or e.g. tactile feelto the viewer such as operator by the configuration of surface graphics,embedded graphics (may still be visible e.g. through the window),surface materials with different surface profiles, general shape, etc.

The obtained structure may be generally kept relatively light, thin andenergy efficient. The optical coupling between the embeddedoptoelectronics such as light sources or sensors and the lightguide maybe strong with low loss and without substantial artifacts. Yet, theassembly may be somewhat simple and compact by construction, whichusually converts into durability and other assets a well. Relativesimplicity of the associated manufacturing process yields benefits ownits own with reference to e.g. the related rather tolerable device andmaterial costs, space, process time, logistic and storage requirements.

The used thermoplastic material may be optimized for various purposesincluding securing electronics in view of the molding process. Yet, themolded material optionally together with other used materials may beconfigured to protect the embedded elements such as electronics frome.g. environmental conditions such as moisture, heat, cold, dirt,shocks, etc.

The expression “a number of” may herein refer to any positive integerstarting from one (1).

The expression “a plurality of” may refer to any positive integerstarting from two (2), respectively.

The ordinal numbers such as “first” and “second” are herein used todistinguish one element from other element, and not to speciallyprioritize or order them, if not otherwise explicitly stated.

The terms “film” and “foil” are herein used generally interchangeably,unless otherwise explicitly indicated.

Different embodiments of the present invention are disclosed in theattached dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Next the present invention will be described in greater detail withreference to the accompanying drawings, in which:

FIG. 1 illustrates one embodiment of a multilayer assembly in accordancewith the present invention.

FIG. 2 is a cross-sectional side view of an embodiment of a multilayerstructure in accordance with the present invention.

FIG. 3 illustrates conceptually one embodiment of a manufacturingprocess for acquiring the multilayer assembly of the present inventionand related elements of the assembly.

FIG. 4 is a flow diagram disclosing an embodiment of a method inaccordance with the present invention.

DETAILED DESCRIPTION

In various embodiments, the masking layer may incorporate a coating,such as a film, on the molded plastic lightguide layer. The maskinglayer may itself be produced on a carrier such as the plastic lightguidelayer using a suitable deposition or other method, for instance, or someother carrier, e.g. a cover layer, to be then provided upon thelightguide layer and preferably secured thereto using e.g. suitablelamination method. Alternatively, the masking layer defined by a film,plate/hoard and/or other element(s) may be formed separately beforehandusing e.g. extrusion or molding and then provided for installation atthe assembly.

In various embodiments, the assembly may indeed contain at least onefurther cover, or ‘top’, layer upon and typically in contact with themasking layer. The cover layer may host or otherwise connect to themasking layer, protect the underlying structures and/or exhibit adesired appearance such as color scheme, graphics, etc.

The cover layer may be provided by at least one cover element such as afilm, plate/board or other coating/cover element on the masking layer.The cover layer may also contain a window for enabling the light emittedby the light sources to pass through to the environment. The window maybe aligned and at least partially overlapping with the window of theunderlying masking layer. It may be of same or different size.

The material(s) of the cover may include plastic, glass, leather,textile, organic or generally fibrous material, for example. Similarconsiderations apply to the masking layer. The material(s) of theoptional cover layer(s) may differ from the material of the maskinglayer. In some embodiments, the material may be substantiallytranslucent or transparent having regard e.g. to the wavelengths emittedby the light sources of the assembly. In some other embodiments, it maybe substantially opaque. The cover and/or masking layer may have e.g.rubber or rubberous surface. The surface material and topology (surfaceforms) may be optimized to provide desired feel and/or aestheticproperties in addition to or instead of e.g. insulation (e.g. moistureand/or thermal) or dampening property. The cover and/or masking layermay be flexible, elastic or stiff/rigid.

In various embodiments, the masking layer and/or other layer/elementbetween the masking layer and the lightguide layer may be at leastlocally reflective having regard to the light emitted by the lightsources to enhance e.g. light propagation within the lightguide insteadof leaks due to absorption or transmission. It may contain reflectivematerial, optionally enabling e.g. specular or diffuse reflectiontherefrom.

In addition to or instead of at least one cover layer, at least onebottom layer defined e.g. by a film or board/plate may be provided onthe second, or ‘bottom’, side of the substrate film using a selectedlamination or deposition technique, for example.

A bottom layer may protect the assembly and/or facilitate its attachmentto a host device, for instance, if the assembly is not secured to thehost via the substrate. The bottom layer or in some scenarios, directlythe substrate, may thus contain attaching features such as adhesivematerial and/or mechanical fixing structure(s) e.g. in the form ofboss/base, dip, hook, recess, etc. for the purpose.

With reference to the paragraphs above, the bottom layer may beconfigured to at least locally reflect light or otherwise control lightpropagation that is preferably at least mainly occurring within thelightguide layer and possibly the substrate film. For the purpose, itmay contain reflective, optionally diffusively or specularly reflective,(surface) material, for example. The bottom layer may be flexible orrigid/stiff.

Thus, depending on the used layer materials, their thicknesses; and e.g.embedded elements, the overall assembly may be generally flexible orrigid/stiff. In some embodiments, its bottom may at least be flexiblethus better conforming to the surface forms of a potential host deviceor support. Alternatively or additionally, the top may be flexibleenabling shaping it e.g. dynamically.

In various embodiments, the substrate film may contain plastic, metal,glass, leather, textile, organic and/or fibrous material (e.g. paper orcardboard). The substrate film may be optically translucent ortransparent having regard to selected wavelength(s). Preferably, thesubstrate film is or at least contains electrically insulating(dielectric) material. The light emitted by the light sources and laterincident on the substrate may be capable of being at least partiallyabsorbed by or penetrating (transmitting) through the substrate filmdepending on the used materials, respective refractive indices andgeneral configuration, e.g. geometry and surface topology, of thearrangement and elements thereof. However, the substrate film may be atleast locally reflective and contain reflective (surface) material e.g.in the form of coating or more thoroughly.

In various embodiments, the substrate has been formed, preferablythrough thermoforming such as pressure forming, vacuum forming orhydroforming, to a desired substantially three-dimensional (non-planar),e.g. curved, angular or undulating, shape relative to its own thicknessprior to or upon the provision of e.g. plastic lightguide layer thereon.The resulting 3d-shape could be several times thicker than the initialfilm. Electronics such as printed electronics and/or mounted componentsmay have been already provided on the substrate prior to forming.Additionally or alternatively, the electronics may have been provided tothe substrate subsequent to forming.

In various embodiments, the window may be defined by an opening, such asa through-hole, flap or cut, in the masking layer and optional furtherlayers thereon. In some embodiments, the masking layer and optionallyfurther layers thereon could include multiple, spatially discretewindows each letting the light of desired wavelength(s), such as thewavelengths of the embedded lights sources, to pass through.

The window(s) in the masking layer and/or other layer(s) establishingpart of the concerned light path may optionally contain translucent,optionally transparent, material having regard to the aforesaidwavelength or band, optionally glass or plastic, such as glazing. It maydefine optically functional element such as a lens, prism or otherrefractive element, and/or a diffractive element, for example.

In some embodiments, the window material may establish a substantiallyplanar piece. The related surfaces may be flat as well.

In some embodiments, however, the top surface (towards the environment,away from the lightguide layer) and/or the opposite bottom surfacefacing towards the lightguide may bear a substantially three-dimensionalshape, e.g. non-planar shape. It may define dome, recess and/orprotrusion shape(s), for example.

The micro-level surface of the window fill may be generally smooth orrough.

A piece of material filling the window opening may also extend at leastpartially through upper layer(s) towards the environment.

The window may exhibit a desired indicative and/or decorative shape,such as at least partial shape of a text, number, symbol, graphicalpattern, and/or figure. Yet, the window material, when applicable, maybe of selected color. In some embodiments, the window may containmultiple different overlapping (in the direction of the surface normalof the multilayer structure, i.e. thickness direction) and/or adjacentmaterials with different properties, e.g. color, transmittance and/orrefractive index.

In various embodiments, the material of the lightguide layer mayestablish at least part of the window filling. The material may definee.g. a protrusion from the lightguide layer that is accommodated in thewindow defined by the masking layer and optionally potential furtherlayers. The lightguide material may in some embodiments also establishat least a part of the exterior (top) surface of the assembly.

The multilayer assembly may be generally substantially planar or flat.The order of magnitude of the width and length of the assembly may thusbe different from the height (the direction in which the layers arestacked), i.e. ‘thickness’, which may be considerably smaller. Forexample, the thickness may be only a few millimeters or less whereas thewidth and length may be several centimeters or more, even considerablymore depending on the embodiment. The thickness may be constant or itmay vary considering e.g. the general shape of a discus that the shapeof the assembly may in some embodiments generally conform to.

In various embodiments, the assembly may be adapted to produce, by theconfiguration of the associated elements, such as light sources,material layers and optional further optically functional elements,uniform lighting via the window from the standpoint of an externalviewer.

As hinted hereinbefore, in various embodiments, the assembly or at leastelement thereof may be configured to diffuse light emitted by the lightsources. Diffusion may soften the light and reduce the contrast betweenbright and dark areas. It may help in obtaining more uniform lightingeffect via the window. For the purpose, the assembly may containspecific diffusers such as diffusive reflector and/or translucentdiffuser, optionally in the form of e.g. plastic film. The diffuser(s)may be dedicated ones or integral with any aforesaid layer. Also theaforementioned non-LOS positioning of light sources relative to themasking layer and window(s) thereof may add to the uniform lighting sothat no light rays may pass the window(s) directly from the lightsources without preceding interactions such as reflections within theassembly. Direct light paths easily cause hotspots visible to theenvironment.

In some embodiments, the assembly or at least element thereof may beconfigured to collimate light and thus include a collimator. Forexample, the element(s) defining the window (fill) material(s) or someother element located functionally prior to the window structure, e.g. areflector, may be arranged to collimate incident light originallyemitted by the light sources and to be outcoupled via the window.

In some embodiments, instead of or in addition to light sources, anumber of light receivers or detectors, such as photodiodes,phototransistors, other suitable photoelectric elements, or e.g.photovoltaic elements (e.g. solar cell) provided on the substrate filmare at least partially embedded through molding inside the establishedplastic layer. These elements are configured to capture or generallysense the light received through the window and/or emitted by the lightsources and propagated within the plastic lightguide layer. Sensing datamay be utilized in adjusting the light sources, for example.

In various embodiments, the light sources or other electronics may havebeen embedded in the material of the plastic lightguide layer rightthrough molding the lightguide material thereon. In some otherembodiments, the ready-made lightguide layer, or at least the concernedportion thereof (e.g. lowest part thereof in case the layer in factcontains several at least initially separate sub-layers, which ispossible) may have been provided with features such as surface forms inthe shape of e.g. recesses or holes, configured to accommodate at leastpart of the protrusions the electronics cause on the substrate. Thelightguide layer comprising optically transmissive material isconfigured to transmit light incoupled from the embedded light sourcesthat are located on the substrate film. The light is preferablyoutcoupled from the lightguide layer through the outer surface thereof,which is the surface on the opposing, other side of the lightguiderelative to the side of the substrate film and light sources embedded inthe lightguide material.

In various embodiments, the electronics included in the assembly, asprovided on the substrate film and/or on further layer(s) or element(s)such as masking layer, may generally comprise at least one featureselected from the group consisting of: conductive trace, printedconductive trace, contact pad, component, integrated circuit (chip),processing unit, memory, communication unit, transceiver, transmitter,receiver, signal processor, microcontroller, battery, light emittingdevice, light sensing device, photodiode, connector, electricalconnector, optical connector, diode, LED, OLED (Organic LED), printedelectronic component, sensor, force sensor, antenna, accelerometer,gyroscope, capacitive switch or sensor, electrode, sensor electrode,printed electrode, printed sensor electrode, and photovoltaic cell.Electronics may be printed by means of printed electronics technology(e.g. screen printing or ink jetting, or other additive methods) and/ormounted. The electronics may be at least partially embedded e.g. in themolded lightguide layer or between different layers. Some features suchas connectors, which may be arranged to supply power to the assembly,for instance, may be at least partially exposed to the environment ofthe assembly.

In case there are several layers (e.g. substrate and masking layer)provided with electronics in the multilayer stack, the layers maybesides structurally via the molded layer, be also functionally. e.g.electrically, connected together to enable e.g. signalling and/orcurrent provision between them.

The connection between the layers may be realized through the use ofconductive elements such as a metal pin, flex circuit, etc. In someembodiments, also wireless connection (e.g. rf or optical) may beapplied.

The (wired) connection may be established subsequent to molding orbefore that using e.g. applicable mold features to protect theconnecting element during molding. Alternatively or additionally, e.g. alead-through may be established for the connecting element duringmolding by appropriate mold feature such as a column preventing thematerial from flowing to the space occupied by it.

As one other alternative or supplementary option, the layers may be e.g.electrically connected together at the edges, optionally via electricalwiring, flex circuit or other conductors, which may enable omitting e.g.the removal of molded material for the connection afterwards from a morecentral area of the established multilayer stack, or arranging aspecific mold feature such as a column for creating a necessarylead-through.

As a further option, the molded material may be machined such as drilledor otherwise processed to arrange a lead-through therein for theconnection and related conductive element(s).

Power supply and/or communication connection to any layer having regardto external electronics or e.g. host device electronics may be arrangedgenerally in a similar fashion, e.g. via side contacts provided at theedge.

As alluded hereinbefore, the cover layer, masking layer, associatedwindow fill material(s), substrate film, bottom layer and/or otherelements of the assembly may have been provided with visuallydistinguishable, decorative/aesthetic and/or informative, features suchas graphical pattern and/or color thereon or therein. The features mayhave been embedded in the assembly below the exterior surfaces thereofand/or provided on the exterior surface thereof. Accordingly, IML(in-mold labeling)/IMD (in-mold decoration) technique is applicable formanufacturing these features.

In various embodiments, the used mold may incorporate surface shapesthat establish corresponding mirror features thereof in the moldedplastic lightguide layer. The shapes/features may include e.g. aprotrusion, grating, boss, boss-base, recess, groove, ridge, hole, or acut.

With reference to the attached figures, FIG. 1 illustrates at 100 oneembodiment of a multilayer assembly in accordance with the presentinvention, in particular exterior thereof.

The depicted, merely exemplary, assembly 100 is generally of somewhatflat or planar discus shape with low side walls, if any. The exteriorsurface of the assembly 100 is at least partially defined by the maskinglayer 106 or optional cover layer(s) 108 thereon. A substantiallytransparent or at least translucent, in this example circular, window116A may be free from material or contain a circular, substantiallyplanar plate of transparent or translucent material, e.g. plastic orglass. In the figure, the window 116A has been depicted also separatelyas indicated by the guiding broken lines leading to the installationposition for illustrative purposes.

A person skilled in the art appreciates the fact the optimum shape maybe determined case-specifically based on optical, size and aestheticobjectives. Accordingly, on the right one still merely exemplary morecomplex option 116B for the window shape is shown.

In other feasible embodiments, the assembly 100 and related elementscould bear more three-dimensional shape thus having also considerablethickness or ‘height’.

The shown assembly 100 has strong (circular) symmetry around itsthickness/height axis but in some other embodiments the assembly or atleast one or more of its components bear different symmetry orsubstantially no symmetry (unsymmetrical) at all.

FIG. 2 shows, via a cross-sectional side view, an embodiment 200 of amultilayer assembly according to the present invention. This mainlyconceptual representation may thus cover e.g. the embodiment of FIG. 1and various other embodiments. Having regard to FIG. 1, the view couldhave been taken along line A-A, for instance. FIG. 3 illustrates, at300, essentially the same or similar embodiment especially from thestandpoint of the manufacturing process and layered construction. InFIG. 3, the illustrated layer thicknesses are only exemplary but mayalso reflect a real-life scenario in terms of relative thicknesses. Forinstance, the substrate 202 may be of film type (with e.g. about 0.1millimeter thickness' while e.g. the lightguide layer 204 may besubstantially thicker, e.g. one or few millimetres, or more.

A substrate 202 has been provided with elements such as electricallyconductive traces (conductors) 210, electronic components 212, 214 suchas light sources 214, light receivers/sensors, integrated circuits, etc.as mentioned hereinbefore at least on first side and related surfacethereof (the top/upper side in the figure). Additionally, such elements314A could be provided on both sides thereof and/or embedded therein,optionally at least partly after molding of a lightguide layer 204 ofpreferably thermoplastic material.

In some applications, instead of molding the lightguide layer 204 itcould be provided otherwise with reference to e.g. a ready-made elementpreferably containing the necessary surface forms such as recesses forreceiving and accommodating at least part of the electronics 212, 214protruding from the first, upper, surface of the substrate 204.

A masking layer 106 may be laminated to or produced on top of thelightguide layer 204. The masking layer 106 contains at least one window116, or in some embodiments, a plurality of windows as discussedhereinbefore, for enabling the light emitted by the light sources 214 tobe transmitted through towards the environment.

The window 116, lightguide layer 204 and light sources 214 (and/or otherrelevant elements, such as light detectors/sensors) have been configuredin terms of e.g. mutual position, materials, dimensions and shape suchthat the light emitted by the sources 214, propagating within thelightguide layer 204 and incident on the window(s) 116 passes throughthe window(s) 116 at least having regard to selected incident angles.

Yet, the configuration is preferably such that the light sources and/orother internal elements, such as additional electronics, remain hiddenfrom the viewer substantially completely or at least within a selectedinspection angle 220 relative to a reference such as the surface normalof the assembly (i.e. the surface normal of the window fill/maskinglayer 106 or of potential top layer 108, or even of lightguide 204 incases where there's no window fill material). The magnitude of theassociated critical angle may be e.g. about 10, 15, 20, 30, 40, 45, 50,60 or more in degrees. In some other embodiments, the reference relativeto which and potentially around which, the above viewing angle isdefined could differ from the above surface normal and may therefore bee.g. a line at a certain angle such as 45 deg angle therefrom.

At least one cover/top layer 108 may be optionally provided and arrangedwith a window 116C that is aligned relative to the window of the maskinglayer 106 so that the light exits the overall assembly, not just thelightguide 204 and masking layer 106, to desired extent. For example,the windows 116, 116C may be substantially superimposed along thethickness/height direction of the assembly.

The windows 116, 116C may generally be of the same or different shapeand optionally dimensions. In the shown scenario the overlapping window116C is larger than window 116, but they could be of the same size e.g.laterally or generally, which is indicated by broken vertical lines 217.The windows may be planar but also considerable 3d shapes (i.e. withcomprehensive thickness dimension) even with thickness variation arepossible. For example, different surface topologies may be applied forimplementing desired optical or other, e.g. insulation, functionalitiesand/or related functional elements, e.g. lenses, prisms, diffractiveelements, etc. therewith.

At least one bottom layer 218 may be optionally provided below thesubstrate 202 on the side opposite to the lightguide layer 204. Thebottom layer 218 may have aesthetic (provided by e.g. graphics, surfaceforms, color, etc.), tactile (e.g. through surface forms, materialselection), protective (material properties, thickness,flexibility/stiffness, hardness, insulation properties, etc.),connective/fixing (e.g. stickiness, adhesion, mechanical such asprotrusion, recess, hook, velcro), conductive (electrically conductivematerial, traces, leads/wires or other conductors) and/or otherfunction.

In some embodiments, the bottom layer(s) 218 are omitted and theassembly 200 is attached via the substrate 202 to the host device orother host element 218. As a further alternative, the assembly 200 maybe of stand-alone element or device type or attach to the host or otherelement via other surface (e.g. via side wall(s)/edges or top surface).

In some embodiments, the assembly 200 forms at least part of a casing orcover of the host device/element. The assembly may be shaped accordinglyto exhibit a generally convex, hollow, receptacle and/or containershape, for example.

The assembly 200 may be configured so as to effectuate internalreflection, preferably total internal reflection based propagation oflight within the lightguide layer 204. The reflection type propagationof light instead of unwanted absorption/leaking may be enhanced throughusing suitable materials. The lightguide layer 204 may have e.g. higherrefractive index than the adjacent masking layer 106, substrate 202,bottom layer/host element surface/protection layer 218 and/or associatedreflector. Yet, the location and geometry of the lightguide layer 204relative to the light sources 214, such as top or side emitting LEDs,may be configured such that the light generally arrives at the materialinterfaces with angles greater than the related critical angle to ensureinternal reflections as being understood by a person skilled in the art.

In some embodiments, e.g. the substrate 202 and lightguide layer 204have substantially similar optical properties in terms of e.g.refractive index. The interface between the two may be then consideredtransparent or substantially non-existing relative to the incident lightand e.g. total internal reflection based propagation thereof within thethen functional combination of lightguide layer 204 and substrate 202.

Having regard to the illumination features of the assembly 200, onegeneral objective may be in providing uniform lighting, or uniform‘brightness’ distribution, via the window 116 towards the environmentwithout hotspots as mentioned hereinearlier. The directivity of thelight (is it e.g. collimated or diffuse) may be determinedcase-specifically as well. For example, diffuse/collimating lens orother feature could be implemented by the properly shaped windowfillings 116, 1160 and/or other elements of the assembly. Embeddedreflecting/mirroring features such as plates, films, or layer surfacescould be utilized for similar purpose.

In addition to the light projected/emitted by the assembly 200(originated by the light sources 214) the perceived illuminationuniformity of the surface also depends on the uniformity of thereflected external light.

Regarding the reflection properties of the window 116, 116C relative toexternal light arriving thereat from the environment of the assembly200, the associated filling (or other element, such as the lightguidelayer 204, of the assembly receiving the external light if there's nowindow filling in the case of e.g. through-hole type window) mayincorporate an outer surface facing the environment. That surface ispreferably ideally or maximally diffusive to reflect such incident lightequally in every direction. This kind of diffusion property may beachieved by elevating surface roughness, for example.

To obtain the desired illumination characteristics such as uniformity,in some embodiments the assembly 200 may be configured in terms ofilluminance of the window 116, 116C or the other element defining atleast part of the exterior surface outcoupling the internallytransmitted light to the environment and potentially reflecting externallight. Constant illuminance of the window 116, 116C from the underlyinglightguide layer 204 may be thus considered as one potential designobjective.

Additionally or alternatively, luminance and/or luminous intensity ofthe window 116, 116C or the other element may be configured to be atleast sufficiently (the appropriate level of sufficiency shall benaturally determined embodiment-specifically by a skilled person)constant.

Generally, the illumination properties of the assembly 200 andparticularly e.g. the window 116, 116C thereof may indeed be determinedby the combination of the used elements related materials, their mutualpositioning, as well as dimensions and shape. The shape may cover bothsurface topology and overall geometry.

FIG. 4 includes a flow diagram 400 disclosing an embodiment of a methodin accordance with the present invention.

At the beginning of the method for manufacturing the multilayerstructure, a start-up phase 402 may be executed. During start-up 402,the necessary tasks such as material, component and tools selection,acquisition, calibration and other configuration activities may takeplace. Specific care must be taken that the individual elements andmaterial selections work together and survive the selected manufacturingand installation process, which is naturally preferably checked up-fronton the basis of the manufacturing process specifications and componentdata sheets, or by investigating and testing the produced prototypes,for example. The used equipment such as molding/IMD (in-molddecoration), lamination, bonding, thermoforming, cutting, drillingand/or printing equipment, among others, may be thus ramped up tooperational status at this stage. Mold(s) may be prepared with necessarysurface forms, etc.

At 404, a preferably flexible substrate film or potentially otherpreferably planar substrate element for accommodating electronics isobtained. A ready-made element of substrate material, e.g. a roll ofplastic film, may be acquired. In some embodiments the substrate filmitself may be first produced in-house by molding, extrusion or othermethods from the desired source material(s). Optionally, the substratefilm is processed. It may be, for example, coated, cut and/or providedwith openings, notches, recesses, cuts, etc. as contemplatedhereinbefore. The initial and/or resulting film may bear e.g.rectangular, square or circular shape. The substrate may be opaque,translucent or substantially transparent having regard to selectedwavelengths of light or generally electromagnetic radiation, such as theoperation wavelengths of the light sources or detectors to be providedthereon.

At 406, a number of conductive traces defining e.g. conductor lines of adesired circuit pattern or circuit design, contact pads (or othercontact areas), etc. for electrically coupling electronic components,are provided on the substrate film, preferably by one or more techniquesof printed electronics with reference to related additive technologies.For example, screen, inkjet, flexographic, gravure or offsetlithographic printing may be utilized. Also further actions cultivatingthe film involving e.g. printing of graphics, visual indicators, etc,may take place here.

At 408, a number of light sources such as LEDs are provided on thesubstrate (surface) optionally with one or more other electroniccomponents. In practice, e.g. ready-made components such as various SMDsmay be attached to the selected contact areas by solder and/oradhesives. Alternatively or additionally, printed electronics technologymay be applied to actually manufacture at least part of the components,such as OLEDs, directly onto the film(s).

In some embodiments, the substrate film may be formed to exhibit adesired 3d-shape (a substantially non-planar shape), preferably throughthermoforming 418 such as vacuum or pressure forming. The substratecontaining thermoformable material may be shaped to better fit the hostdevice or use scenario. Additionally or alternatively, thermoformingcould even take place after molding 410 in case the already-establishedmultilayer stack is designed to survive such processing. Having regardto forming techniques, e.g. pressure forming may be applied to providethe substrate with very precise, sharp details. Pressure forming may begenerally preferred when the substrate lacks (through-)holes that couldenable undesired flow and resulting pressure drop via them.

In some embodiments, a number of sub-assemblies ofelectronics/sub-substrates may be provided as such to the primarysubstrate at 409 and secured by adhesive, for instance.

At 410, at least one thermoplastic layer establishing a lightguide forthe light emitted by the light sources is molded upon the first side ofthe substrate film and at least part of the electronics thereon, such astraces and a number of electronic components. Preferably the lightsources are at least partially embedded within the molded material.Accordingly, the optical contact between them and the molded lightguidelayer will be excellent with low optical coupling losses. In practice,the substrate film may be used as an insert in an injection moldingprocess. The first side and associated surface of the substrate elementmay be, in some embodiments, left with one or more areas, such asborders, free from the molded plastics. In some embodiments, both sidesof the substrate film may be provided with molded layer(s). Thethermoplastic material used is preferably at least translucent. It maystill exhibit at least one color.

In case two films are used, one designated as the substrate and theother as e.g. the masking layer or a layer to be located below it in theassembly stack, both of them may be inserted in their own mold halves sothat the plastic layer is injected between them. The other film may havebeen optionally provided with electronics (e.g. printed electronics,such as traces or components, sensor electrodes and/or mountedcomponents) prior to molding e.g. during the execution of items 406, 408and/or formed prior to molding. The electronics and/or other elementsmay be provided e.g. on the side of the other film facing the substratefilm and molded plastics.

The plastic may be injected via one or more locations e.g. from theside(s) of the film(s). Thus e.g. edge injection and/or hole injection(plastic injection between the films through one or more holes in thefilm(s)) may be applied. Alternatively, the other film for establishinge.g. the masking layer could be attached to an aggregate of thesubstrate film and plastic lightguide layer afterwards by suitablelamination technique.

The other film could be provided with at least one hole for theafore-discussed window(s). The hole may result from cutting, drilling,carving, stamping or etching operation, for instance. During molding,the thermoplastic molding material may then enter the hole from eitheror both sides, optionally also proceeding to the other side of the film,and establish at least part of the window till for at least theconcerned film.

In some embodiments, there is no through-hole ready in the other filmprior to the molding. The film may still optionally have e.g. a thinnedor otherwise weakened (formed using e.g. one of the abovementionedoperations) spot at the target location of the window to facilitatewindow formation during molding due to the pressure of the moldedmaterial. In some embodiments, the mold surface contacting the otherfilm may have a surface feature such as a recess, perforated area, flapor pinhole thereon corresponding to the target location of the window inthe other film, which may facilitate forming and/or filling the windowduring molding. The feature thus matching and facing the desired area ofthe window in the other film may further enable the molded material toflow via the window to the other side (i.e. mold/exterior side) of theother film.

Having regard to few examples of the applicable material selections, thesubstrate film and/or potential further film(s) or material layers maysubstantially consist of or comprise at least one material selected fromthe group consisting of: polymer, thermoplastic material, PMMA(Polymethyl methacrylate), Poly Carbonate (PC), polyimide, a copolymerof Methyl Methacrylate and Styrene (MS resin), glass, organic material,fibrous material, Polyethylene Terephthalate (PET), and metal.

The feasible molding methods include e.g. injection molding. In case ofseveral plastic materials, they may be molded using a two-shot orgenerally multi-shot molding method. A molding machine with multiplemolding units may be utilized. Alternatively, multiple machines or asingle re-configurable machine could be used for sequentially providingseveral materials.

The first side and thus the associated first surface of the substratehas thus been at least partially, having regard to the related surfacearea, overmolded by plastic, preferably and typically thermoplastic,material. Optionally, several overmolding-applicable materials may beutilized to establish one or more molded layers, e.g. adjacent layerslying side-to-side on the first side of the substrate and/or forming astack of multiple superposed layers thereon.

The (thermo)plastic material used to establish the molded layer(s)comprises optically substantially opaque, transparent or translucentmaterial having regard to selected wavelengths enabling e.g. lightemitted by the embedded light sources, such as visible light, to passthrough it with negligible loss. The sufficient transmittance of thematerial at selected wavelengths may be about 60%, 70%, 75%, 85%, 90% or95% or higher, for example, depending on the embodiment. Possiblefurther molded (thermo)plastic material such as material establishingthe masking layer may be substantially opaque or translucent.

The plastic layer(s) provided by the overmolding procedure may generallyincorporate e.g. elastomeric resin. In more detail, the layer(s) mayinclude one or more thermoplastic materials that include at least onematerial selected from the group consisting of: PC, PMMA, ABS(Acrylonitrile butadiene styrene), PET, nylon (PA, polyamide),polypropylene (PP), polystyrene ((PPS), and MS resin.

At 412, further layer(s) such as the masking layer if not alreadypresent with reference to the previous paragraphs, may be finallyprovided to the assembly. Provision may include direct manufacturingthrough e.g. molding, deposition/other coating method, and attaching. Awindow-defining cut or hole may be provided in the masking and potentialfurther layers by drilling, carving, sawing, etching, cutting (e.g. withlaser or mechanical blade), or using any other feasible processingmethod as being understood by a person skilled in the art.Alternatively, the layer(s) may be produced with ready-made windowfeature through molding, for example.

Suitable lamination techniques for fixing various layer(s) to theassembly utilize e.g. adhesive, elevated temperature and/or pressurebased bonding.

Regarding the resulting overall thickness of the obtained stackedstructure, it heavily depends on the used materials and related minimummaterial thicknesses providing the necessary strength in view of themanufacturing and subsequent use. These aspects have to be considered oncase-by-case basis. For example, the overall thickness of the structurecould be about 1 mm, but considerably thicker or thinner embodiments arealso feasible.

Item 414 refers to possible post-processing tasks and attachment to ahost device or element.

At 416, method execution is ended.

The scope of the present invention is determined by the attached claimstogether with the equivalents thereof. A person skilled in the art willappreciate the fact that the disclosed embodiments were constructed forillustrative purposes only, and other arrangements applying many of theabove principles could be readily prepared to best suit each potentialuse scenario. For example, in some applications instead of substantiallyopaque masking layer, translucent (e.g. diffusive) material could beused therein. The translucent material would still hinder or preventdirect light propagation through the masking layer.

The invention claimed is:
 1. A multilayer assembly for an electronicdevice comprises: a flexible substrate film configured to accommodateelectronics on at least first side thereof, said film having the firstside and a second side, a number of conductive traces printed by meansof printed electronics technology on the first side of the substratefilm, a number of light sources provided on the first side of thesubstrate film and configured to emit light of predetermined frequencyor frequency band, including or substantially limiting to visible light,a molded plastic lightguide layer provided onto the first side of thesubstrate film and at least partially embedding the light sources, theplastic lightguide layer being of optically at least translucent,optionally substantially transparent, material having regard to thepredetermined frequency or band, wherein the plastic lightguide layer isconfigured to transmit light emitted by the embedded light sources sothat the transmitted light propagates within the lightguide layer and isoutcoupled from the plastic lightguide layer via an outer surfacethereof substantially opposite to the embedded light sources, a maskinglayer provided on the outer surface of the plastic lightguide layer,containing substantially opaque material to block external view of atleast some internals of the multilayer assembly including the lightsources, wherein the masking layer defines a window for letting thelight emitted by the embedded light sources and propagated within theplastic lightguide layer to pass through the masking layer towards theenvironment, at least one diffusor located between the light sources andthe environment, a bottom layer on the second side of the substratefilm, and another diffusor, wherein the bottom layer comprises theanother diffusor, the light sources, masking layer and related windowbeing mutually configured such that there is substantially no directline-of-sight (LOS) path at least within a selected viewing angle fromoutside the assembly, including zero angle from the surface normal ofthe masking layer, to the light sources and optionally furtherelectronics through the window.
 2. The assembly of claim 1, furthercomprising a protective cover layer on the masking layer.
 3. Theassembly of claim 2, wherein the cover layer is of substantiallyoptically transparent material having regard to the frequency orfrequency band of the light sources, or defines a window of no material,such as a through-hole, or of substantially optically translucent ortransparent material having regard to the frequency or band of the lightsources.
 4. The assembly of claim 1, wherein the bottom layer containsor is established by an attaching feature, optionally including adhesiveor a mechanical fixing structure, for securing the assembly to a hostdevice or host element.
 5. The assembly of claim 1, wherein at least thesubstrate film appears formed to a three-dimensional, non-planar, shape.6. The assembly of claim 1, wherein the window is a through-hole.
 7. Theassembly of claim 1, wherein the window includes optically substantiallytranslucent or transparent material having regard to said frequency orband.
 8. The assembly of claim 1, wherein the window defines the atleast one diffusor.
 9. The assembly of claim 1, wherein the lightguidelayer comprises said at least one diffusor.
 10. The assembly of claim 1,wherein the masking layer comprises said at least one diffusor.
 11. Theassembly of claim 1, wherein the at least one diffusor is providedthrough elevated surface roughness.
 12. The assembly of claim 1, whereinthe at least one diffusor is a dedicated diffusive layer.
 13. Theassembly of claim 1, wherein the at least one diffusor comprisesreflective material.
 14. The assembly of claim 1, wherein the at leastone diffusor comprises a plastic film.
 15. The assembly of claim 1,wherein the at least one diffusor is an embedded reflecting featureselected from the group of a plate, film, or layer surface.
 16. Theassembly of claim 1, wherein the window defines at least one illuminatedelement selected from the group consisting of: graphical pattern, text,symbol, number, and figure.
 17. The assembly of claim 1, wherein theilluminance, luminance or luminous intensity associated with the windowis substantially constant to provide uniform illumination to theenvironment.
 18. The assembly of claim 1, wherein the substrate filmcontains optically substantially translucent or transparent materialhaving regard to said frequency or band.
 19. The assembly claim 1,configured for substantially internal reflection based propagation oflight therewithin between the light sources and the window.
 20. Theassembly of claim 1, wherein the substrate film includes at least onematerial selected from the group consisting of: polymer, thermoplasticmaterial, PMMA (Polymethyl methacrylate), Poly Carbonate (PC),polyimide, a copolymer of Methyl Methacrylate and Styrene (MS resin),glass, organic material, fibrous material, Polyethylene Terephthalate(PET), and metal.
 21. The assembly of claim 1, wherein the plasticlightguide layer includes at least one material selected from the groupconsisting of: PC, PMMA, ABS, PET, nylon (PA, polyamide), polypropylene(PP), polystyrene (GPPS), and MS resin.
 22. The assembly of claim 1,wherein the electronics located on the substrate comprise at least oneelement selected from the group consisting of: conductive trace, printedconductive trace, contact pad, component, integrated circuit (chip),processing unit, memory, communication unit, transceiver, transmitter,receiver, signal processor, microcontroller, battery, light emittingdevice, light sensing device, photodiode, connector, electricalconnector, optical connector, diode, OLED (Organic LED), printedelectronic component, sensor, force sensor, antenna, accelerometer,gyroscope, capacitive switch or sensor, electrode, sensor electrode,printed sensor electrode, and photovoltaic cell.
 23. The assembly ofclaim 1, wherein the at least one diffusor comprises a lens.
 24. Amethod of establishing a multilayer assembly for an electronic devicecomprising: obtaining a flexible substrate film configured toaccommodate electronics on at least first side thereof, said film havingthe first side and a second side, printing, by means of printedelectronics technology, a number of conductive traces on the first sideof the substrate film, providing a number of light sources on the firstside of the substrate film, said light sources being configured to emitlight of predetermined frequency or frequency band, molding a plasticlightguide layer onto the first side of the substrate film and therebyat least partially embedding the light sources, the plastic lightguidelayer being of optically at least translucent material having regard tothe predetermined frequency or band of light, whereupon the plasticlightguide layer is configured to transmit light emitted by the embeddedlight sources so that the transmitted light propagates within thelightguide layer and is outcoupled from the lightguide layer via anouter surface thereof substantially opposite to the embedded lightsources, and providing a masking layer on the outer surface of thelightguide layer containing substantially opaque material to blockexternal view of at least some internals of the multilayer assemblyincluding the light sources, wherein the masking layer defines a windowfor letting the light emitted by the embedded light sources andpropagated within the lightguide layer to pass through the masking layertowards the environment, wherein at least one diffusor is providedbetween the light sources and the environment, wherein the multilayerassembly further includes: a bottom layer on the second side of thesubstrate film, and another diffusor, wherein the bottom layer comprisesthe another diffusor, the light sources, masking layer and relatedwindow being mutually configured such that there is substantially nodirect line-of-sight path at least within a selected viewing angle fromoutside the assembly to the light sources and optionally furtherelectronics through the window.
 25. The method of claim 24, wherein afurther film for establishing either the masking layer or a layerbetween the masking layer and lightguide layer, and the substrate filmare provided within a mold, each against opposing mold halves, andthermoplastic material for forming the plastic lightguide layer ismolded between the two films.
 26. The method of claim 25, wherein thefurther film contains or is processed to contain a through-hole for thewindow.
 27. The method of claim 24, wherein the further film contains oris processed to contain a surface feature, optionally a thinned portion,pinhole, perforated portion or a flap, substantially at the targetlocation of the window to enable window formation during the moldingprocedure due to the associated pressure introduced to the feature. 28.The method of claim 24, wherein the mold contains a recess or holealigned so as to substantially match the location of the window.